Impact of Proportional Representation on Party Dynamics

In the United States, the electoral system used for congressional elections has a profound impact on both voter behavior and party representation. Understanding the consequences of different electoral systems is vital for analyzing the dynamics of elections. One arrangement, the winner-takes-all system, is employed in most states during the Electoral College process for presidential elections. However, alternative systems, such as proportional representation, can significantly alter election outcomes and foster multi-party systems. Given these variations, consider the following scenario: If the United States adopted a proportional representation system for congressional elections, what would likely be the most significant change compared to the current plurality system?